This control loop is also indicated on the PFD of Figure 1.5. These are a high-level alarm (LAH) and a low-level alarm (LAL), and they receive the same signal from the level transmitter as does the controller. In order to warn operators of potential problems, two alarms are placed in the control room. From the LIC, an electrical signal is sent to an instrument (LY) that computes the correct valve position and in turn sends a pneumatic signal (designated by a solid line with cross hatching) to activate the control valve (LCV). This LIC is located in the control room on the control panel or console (as indicated by the horizontal line under LIC) and can be observed by the operators. A level transmitter (LT) also located on V-104 sends an electrical signal (designated by a dashed line) to a level indicator and controller (LIC). The sequence of instrumentation is as follows:Ī level sensing element (LE) is located on the reflux drum V-104. The flowrate of this stream is controlled by a control valve that receives a signal from a level measuring element placed on V-104. Instrument Located on Back of Panel in Control RoomĬonsider the benzene product line leaving the right-hand side of the P&ID in Figure 1.7. Instrument Located on Front of Panel in Control Room Conventions Used for Identifying Instrumentation on P&IDs (ISA standard ISA-S5-1, ) Example 1.9 illustrates the interpretation of instrumentation and control symbols. Table 1.10 summarizes the conventions used to identify information related to instrumentation and control. The circular flags on the diagram indicate where the information is obtained in the process and identify the measurements taken and how the information is dealt with.
This includes the information to be recorded and used in process control loops. The key identifying the utility connections is shown in a table on the P&ID.Īll process information that can be measured in the plant is shown on the P&ID by circular flags. The number within the box identifies the specific utility. Utility connections are identified by a numbered box in the P&ID. 1, Chapter G.1.5, AIChE copyright © 1986 AIChE, all rights reserved)
#PIPE DRAFTING AND DESIGN THIRD EDITION EXERCISE ANSWERS SERIES#
Piping and Instrumentation Diagram for Benzene Distillation (adapted from Kauffman, D., Flow Sheets and Diagrams, AIChE Modular Instruction, Series G: Design of Equipment, series editor J. When possible, the physical size of the larger-sized unit operations is reflected by the size of the symbol in the diagram.įigure 1.7. As an alternative, each pipe can be numbered, and the specifics of every line can be provided in a separate table accompanying this diagram. The P&ID presented in Figure 1.7 provides information on the piping, and this is included as part of the diagram. Figure 1.7 is a representative P&ID for the distillation section of the benzene process shown in Figure 1.5.
Indicators Recorders Controllers Show Instrument LinesĮntrance Utilities Exit Utilities Exit to Waste Treatment FacilitiesĮach PFD will require many P&IDs to provide the necessary data.
Spare Units Parallel Units Summary Details of Each Unitįor Piping-Include All Lines Including Drains and Sample Connections, and Specify Conventions in Constructing Piping and Instrumentation Diagrams Exclusions from Piping and Instrumentation Diagram The general conventions used in drawing P&IDs are given in Table 1.9. The P&ID includes every mechanical aspect of the plant except the information given in Table 1.8. The piping and instrumentation diagram (P&ID), also known as mechanical flow diagram (MFD), provides information needed by engineers to begin planning for the construction of the plant. Piping and Instrumentation Diagram (P&ID)
Analysis, Synthesis and Design of Chemical Processes, 4th Editionġ.3.
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